1. Field of the Invention
The present invention relates to a dynamic random access memory (hereinafter referred to as a DRAM). More particularly, it relates to a DRAM for increasing a data output driver current which shares pull-up transistors and pull-down transistors of the unused 8 data output buffers with other pull-up transistors and other pull-down transistors of the used 8 data output buffers, in case that 8 pins are only used in a product having 16 data pins.
2. Description of the Prior Art
In general, in order to manufacture various products in a DRAM, the number of data inputs or the number of data outputs is controlled by using a bonding option or a metal option. For example, 16M DRAM determines whether the number of data is set to 8 (i.e., it is indicated as a mark x8) or 16 (i.e., it is indicated as another mark x16) in one chip by using the bonding option or the metal option.
In this case, 16 data bus lines are basically needed to the inside of the chip, and 16 data pins are also needed thereto. That is, 16 data bus lines and 16 data pins are all used in the case x16, but 8 data bus lines and 8 data pins are selectively used among them in the other case x8.
FIG. 1 depicts a data path of DRAM having 16 data output pins (i.e., x16). As shown in FIG. 1, one data output buffer is connected to each data output pin DQi. Each data output buffer includes a read transmission circuit 12 which receives a read data from a data bus sense amplifier 11 as an input, and controls an operation of the data output buffer.
In this case, 16 data pins are all used in case x16, or 8 data pins among the 16 data pins are selectively used in case x8.
However, in the aforementioned DRAM, the most general method for increasing a data output drive current IOL/IOH is to increase the sizes of the last pull-up transistor and the last pull-down transistor. In this case, the size of a chip increases by an increase of the layout area. If a first peak current consumed while a first product x16 outputs 16 data is compared with a second peak current consumed while a second product x8 outputs 8 data after the sizes of the last pull-up and pull-down transistors are uniformly enlarged to increase the data output drive current IOL/IOH, the first peak current consumed in the product x16 is about twice the value of the second peak current consumed in the product x8. Accordingly, such peak current may incur a power noise.